The feeding of an infant from a nipple-equipped, hard-walled bottle often results in air intake by the infant. The air intake occurs when air passes through the nipple orifice during feeding to equalize the reduced air pressure inherently occurring within the bottle as the liquid is removed. Air intake by the infant can cause discomfort, and, when this intake becomes excessive, can produce colic-like symptoms.
One infant feeding system that now is in common use employs thin plastic bags which collapse during feeding so that minimal air intake occurs. This system, however, is considered by some to be undesirable because it requires the replacement of the plastic bag for each feeding since the bag is not readily sterilizable after each use.
Various pressure equalizing valve-like means for use in association with hard-walled infant feed bottles have previously been proposed with the objective of reducing air intake by an infant.
However, so far as now known, all such previous valved bottle proposals have not met the basic criteria needed for general commercial practicality, such as:
1) equalizing internal bottle air space pressure at a rate which is substantially equal to the rate at which the internal pressure changes as liquid is withdrawn; and
2) achieving a substantially liquid-tight seal (without weeping) when a bottle containing a feeding liquid is placed in a (temporary) upright storage (or resting) position.
In addition, such a bottle must be fully sterilizable, capable of repeated reuse and resterilization, reliable, simple and capable of manufacture at a low cost.
A substantial and long-felt need exists in the infant feeding bottle field for a practical valved, hard-walled bottle structure. The present invention is believed to meet both the foregoing criteria and this need.